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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Scaling of cross sections for K-electron capture by high-energy protons and alpha-particles from the multielectron atoms

Electron capture by protons from H, He, and the K shell of Ar, and electron capture by alpha particles from He are considered. Using the experimental data, a function of the capture cross section is formed. It is shown that when this function is plotted versus the inverse of the collision energies, at high energies a straight line is obtained. At lower energies the line is concave up or down, depending on the charge of the projectile and/or the effective charge and the ionization potential of the electron that is being captured. The plot can be used to predict cross sections where experimental data are not available, and as a guide in future experiments. High-energy scaling formulas for K-electron capture by low-charge projectiles are given.

Omidvar, K.↗
NASA NTRS1993

Can Bose condensation of alpha particles be observed in heavy ion collisions?

Using a fully self-consistent quantum statistical model, we demonstrate the possibility of Bose condensation of alpha particles with a concomitant phase transition in heavy ion collisions. Suggestions for the experimental observation of the signature of the onset of this phenomenon are made.

Tripathi, Ram K.↗
NASA NTRS1995

Depth Measurements Using Alpha Particles and Upsettable SRAMs

A custom designed SRAM was used to measure the thickness of integrated circuit over layers and the epi-layer thickness using alpha particles and a test SRAM. The over layer consists of oxide, nitride, metal, and junction regions.

upsettable SRAMs↗
NASA NTRS1979

Low-altitude measurements of precipitating protons, alpha particles, and heavy ions during the geomagnetic storm on March 26-27, 1976

During the geomagnetic storm of March 16-17, 1976, observations were made of precipitating protons, alpha particles, and heavy ions by two counter telescopes aboard the low-altitude S3-2 satellite. These observations are presented in this paper and their significance discussed. Briefly, a two-zone precipitation region is observed on the nightside, at L equals 2.7 and L equals 4.0 with an alpha/p ratio of about 0.008 in the low-latitude region and about 0.0009 at higher latitude at 0.4 MeV/necleon. The heavier ions, CNO nuclei, are seen in the low-latitude zone with a CNO/alpha ratio of about 0.056 at 0.25 MeV/nucleon.

Scholer, M.↗
NASA NTRS2002

Nucleon-Alpha Particle Disequilibrium and Short-Lived r-Process Radioactivities

r-Process yields can be extremely sensitive to expansion parameters when a persistent disequilibrium between free nucleons and alpha particles is present. This may provide a natural scenario for understanding the variation of heavy and light r-process isotopes in different r-process events. Additional information is contained in the original extended abstract.

Meyer, B. S.↗
NASA NTRS1972

Scattering of 42-MeV alpha particles from Cu-65

The extended particle-core coupling model was used to predict the properties of low-lying levels of Cu-65. A 42-MeV alpha particle cyclotron beam was used for the experiment. The experiment included magnetic analysis of the incident beam and particle detection by lithium-drifted silicon semiconductors. Angular distributions were measured for 10 to 50 degrees in the center of mass system. Data was reduced by fitting the peaks with a skewed Gaussian function using a least squares computer program with a linear background search. The energy calibration of each system was done by pulsar, and the excitation energies are accurate to + or - 25 keV. The simple weak coupling model cannot account for the experimentally observed quantities of the low-lying levels of Cu-65. The extended particle-core calculation showed that the coupling is not weak and that considerable configuration mixing of the low-lying states results.

Stewart, W. M.↗
NASA NTRS1994

Making A D-Latch Sensitive To Alpha Particles

Standard complementary metal oxide/semiconductor (CMOS) D-latch integrated circuit modified to increase susceptibility to single-event upsets (SEU's) (changes in logic state) caused by impacts of energetic alpha particles. Suitable for use in relatively inexpensive bench-scale SEU tests of itself and of related integrated circuits like static random-access memories.

Buehler, Martin G.↗
NASA NTRS1996

Alpha-Particle Gas-Pressure Sensor

An approximate model was developed to establish design curves for the saturation region and a more complete model developed to characterize the current-voltage curves for an alpha-particle pressure sensor. A simple two-parameter current-voltage expression was developed to describe the dependence of the ion current on pressure. The parameters are the saturation-current pressure coefficient and mu/D, the ion mobility/diffusion coefficient. The sensor is useful in the pressure range between 0.1 and 1000 mb using a 1 - mu Ci(241) Am source. Experimental results, taken between 1 and up to 200 mb, show the sensor operates with an anode voltage of 5 V and a sensitivity of 20 fA/mb in nitrogen.

Buehler, M. C.↗
NASA NTRS2006

Two Years of Chemical Sampling on Meridiani Planum by the Alpha Particle X-Ray Spectrometer Onboard the Mars Exploration Rover Opportunity

For over two terrestrial years, the Mars Exploration Rover Opportunity has been exploring the martian surface at Meridiani Planum using the Athena instrument payload [1], including the Alpha Particle X-Ray Spectrometer (APXS). The APXS has a small sensor head that is mounted on the robotic arm of the rover. The chemistry, mineralogy and morphology of selected samples were investigated by the APXS along with the Moessbauer Spectrometer (MB) and the Microscopic Imager (MI). The Rock Abrasion Tool (RAT) provided the possibility to dust and/or abrade rock surfaces down to several millimeters to expose fresh material for analysis. We report here on APXS data gathered along the nearly 6-kilometers long traverse in craters and plains of Meridiani.

Bruckner, J.↗
NASA NTRS2006

The Alpha Particle X-Ray Spectrometer (APXS): Results from Gusev Crater and Calibration Report

The chemical composition of rocks and soils on Mars analyzed during the Mars Exploration Rover Spirit Mission was determined by X-ray analyses with the Alpha Particle X-Ray Spectrometer (APXS). Details of the data analysis method and the instrument calibration are presented. Measurements performed on Mars to address geometry effects and background contributions are shown. Cross calibration measurements among several instrument sensors and sources are discussed. An unintentional swap of the two flight instruments is evaluated. New concentration data acquired during the first 470 sols of rover Spirit in Gusev Crater are presented. There are two geological regions, the Gusev plains and the Columbia Hills. The plains contain soils that are very similar to previous landing sites on Mars. A meteoritic component in the soil is identified. Rocks in the plains revealed thin weathering rinds. The underlying abraded rock was classified as primitive basalt. One of these rocks contained significant Br that is probably associated with vein-filling material of different composition. One of the trenches showed large subsurface enrichments of Mg, S, and Br. Disturbed soils and rocks in the Columbia Hills revealed different elemental compositions. These rocks are significantly weathered and enriched in mobile elements, such as P, S, Cl, or Br. Even abraded rock surfaces have high Br concentrations. Thus, in contrast to the rocks and soils in the Gusev Plains, the Columbia Hills material shows more significant evidence of ancient aqueous alteration.

Gellert, R.↗
NASA NTRS1983

Thermal and suprathermal protons and alpha particles in the earth's plasma sheet

Detailed proton energy spectra in the quasi-stable distant plasma sheet over the energy range from approximately 13 keV to approximately 130 keV are presented. These spectra are compared with spectra of simultaneously measured alpha particles in the energy range from approximately 30 keV/Q to approximately 130 keV/Q. The proton spectra are then extended into the higher energy range up to approximately 1 MeV, thereby supplementing the study of Sarris et al. (1981). The temporal behavior of the spectra in the higher energy range is discussed. It is found that below about 16 keV the proton spectra can be represented by a Maxwellian distribution; above this level, a suprathermal tail is found that cannot be represented by a single power law.

Ipavich, F. M.↗
NASA NTRS2014

Mapping alpha-Particle X-Ray Fluorescence Spectrometer (Map-X)

Many planetary surface processes (like physical and chemical weathering, water activity, diagenesis, low-temperature or impact metamorphism, and biogenic activity) leave traces of their actions as features in the size range 10s to 100s of micron. The Mapping alpha-particle X-ray Spectrometer ("Map-X") is intended to provide chemical imaging at 2 orders of magnitude higher spatial resolution than previously flown instruments, yielding elemental chemistry at or below the scale length where many relict physical, chemical, and biological features can be imaged and interpreted in ancient rocks.

CCD Camera↗
NASA NTRS1995

Alfven waves, alpha particles, and pickup ions in the solar wind

Past studies of the properties of Alfven waves in the solar wind have indicated that (1) the amplitude of the velocity fluctuations is almost always smaller than expected on the basis of the amplitude of the field fluctuations, even when the anisotropy of the plasma is taken into account, and (2) the alpha particles do not participate in the wave motions because they 'surf' on the waves carried by the proton fluid. Ulysses data are used to demonstrate that (1) the discrepancy between the velocity and field fluctuations is greater at high heliographic latitudes than in the ecliptic plane, and (2) the alphas do participate in the waves, being either in phase or out of phase with the proton motions depending on whether the differential flow speed between the alphas and protons is greater than or less than the 'observed' wave speed, B(sub o)(delta v squared / delta B squared)exp 1/2, as determined from the ratio of the amplitudes of the velocity and magnetic fluctuations. It is proposed that the modification of Alfven wave propagation speed is due to pressure anisotropies resulting from asymmetric distributions of interstellar pickup ions. If the proposed explanation is correct, it indicates that scattering of pickup ions onto a (bi)spherical shell may not be as complete as generally supposed.

Goldstein, B. E.↗
NASA NTRS1995

Alfven Waves, Alpha Particles, and Pickup Ions in the Solar Wind

Past studies of the properties of Alfven waves in the solar wind have indicated that the amplitude of the velocity fluctuations is almost always smaller than expected on the basis of the amplitude of the field fluctuations, even when plasma anisotropy is taken into account. Also, the alpha particles often do not participate in the wave motions because they "surf" on the proton fluid waves.

Alfven↗
NASA NTRS1978

Determination of oxygen in silicon and carbide by activation with 27.2 meV alpha particles

The Si sample was polished on one side, and on the other side Ni was applied chemically and soldered with Pb to a water cooled Cu substrate. Optical quartz standard was fixed from the other side. Si carbide samples were soldered to a substrated with In. The prepared samples were irradiated in a cyclotron with a 27.2 MeV alpha particle beam. The layers were removed from the Si and Si carbide samples by grinding and the positron activity of F-18(t sub 1/2 110 min) was measured by using a gamma, gamma coincidence spectrometer with two NaI(TI) crystals. For analysis of Si carbide, the activity decay curve of the samples was recorded to find the contribution of the positron activity of Cu-65(t sub 1/2 12.9 hr) which formed from Ni impurity on irradiation.

Dolgolenko, A. P.↗
NASA NTRS1985

Determination of primary energy in nucleus-nucleus collisions and the high P(sub)T tail of alpha-particles

A determination of primary energy is required in order to study the energy dependence of meson multiplicity in A-A collisions in cosmic rays. Various procedures which estimate the energy of a primary nucleus from its interaction were investigated. An average of two methods were used, one using the pions and wounded protons and the other using spectator protons and alpha particles. The high P sub T tail observed for Z = 2 fragments requires a modification of the latter method.

Freier, P. S.↗
NASA NTRS1995

Gas Pressure Gauge Based on Alpha-Particle Induced Ion Currents

The use of ionization currents for measuring pressure was first demonstrated in the late 1940's. The early gauges operated at high voltages and used rather large ion sources. The ionization gauge is actually a densitometer that is sensitive to the temperature and pressure of the gas in the chamber. This report describes the use of low voltages and small ion sources in the development of a prototype.

transducers gas pressure gauge alpha particles ion↗